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r-process

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Contact: F.X.Timmes
my one page vitae,
full vitae,
research statement, and
teaching statement.
Supernova fallback: a possible site for the r-process (2006)

In this paper by Fryer et al we investigate the mass ejected by fallback in a supernova explosion. Trans-iron element production beyond the second peak is made possible by a rapid (< 1 ms) freezeout of α-particles that leaves behind a large nucleon (including protons!) to r-process seed ratio. This rapid phase is followed by a relatively long (≤ 15 ms) simmering phase at < 2x109 K, which is a consequence of the hydrodynamic trajectory of the turbulent flows in the fallback outburst. During the slow phase, heavy elements beyond the second peak are first made through rapid capture of both protons and neutrons. The flow stays close to the valley of stability during this phase. After freezeout of protons the remaining neutrons cause a shift to short-lived isotopes, as is typical for the r-process. A low electron fraction is not required in this model; however, the detailed final distribution is sensitive to the electron fraction. Our simulations suggest that supernova fallback is a viable alternative scenario for the r-process.

Brad Meyer's paper", "The r-Process without Excess Neutrons" is highly relevant to this scenario.

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ejecta after fallback
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abundance pattern of ejecta
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n, p, α evolution
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abundances at 0.170 s
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abundances at 0.171 s
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abundances at 3.5 s
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meyer ratio (unpublished)
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abundance movie, 1.5 MB, mp4